The present invention relates to an image display apparatus, and more particularly relates to a thin image display apparatus used for a video camera and the like.
Conventionally, cathode ray tubes have been used mainly as image display apparatuses for color televisions, personal computers and the like. However, in recent years, image display apparatuses have been required to be improved for space saving, for portability or for some other demands. In order to satisfy these demands, various types of thin image display apparatuses have been developed and commercialized.
Under these circumstances, various types of thin image display apparatuses have been researched and developed recently. In particular, liquid crystal displays and plasma displays have been developed actively. The liquid crystal displays have been applied to various types of products such as portable personal computers, portable televisions, video cameras, car-navigation systems and the like. In addition to that, the plasma displays have been applied to products such as large-scale displays, for example, 20 inch-displays or 40-inch displays.
However, there are some problems for the displays. A liquid crystal display has a narrow visual angle and a slow response. Regarding a plasma display, high brightness can""t be obtained and the consumed electricity is large. A thin image display apparatus called a field emission image display apparatus has attracted considerable attention to solve these problems. The field emission image display apparatus uses field emission, i.e. a phenomenon in which electrons are emitted in a vacuum at room temperature. The field emission image display apparatus is a spontaneous luminescent type, and therefore it is possible to obtain a wide visual angle and high brightness. The spontaneous luminescent type apparatus does not require back lighting, and thus, it consumes less electric power.
An image display apparatus disclosed in Unexamined Published Japanese Patent Application (Tokkai-Hei) No. 2-33839 is known as a flat spontaneous light emission type image display apparatus with high-quality images. This is different from the above-mentioned field emission image display apparatus in the structure but uses a linear hot cathode.
FIG. 9 is a perspective exploded view showing a conventional image display apparatus. The conventional image display apparatus comprises a back electrode 100, a linear cathode 101, an electron beam-attracting electrode 102, a control electrode 103, a first focusing electrode 104, a second focusing electrode 105, a horizontal deflecting electrode 106, a vertical deflecting electrode 107, a front glass container 109a having a fluorescent layer 108 on the inner surface, and a rear glass container 109b. The back electrode 100, the linear cathode 101, the electron beam-attracting electrode 102, the control electrode 103, the first focusing electrode 104, the second focusing electrode 105, the horizontal deflecting electrode 106 and the vertical deflecting electrode 107 are contained between the rear glass container 109band the front glass container 109a (the fluorescent layer 108 side), and the space where those components are contained between the glass containers (109a, 109b) is maintained under a vacuum.
In the image display apparatus, electron beams are formed in a matrix by the linear cathode 101 and the electron beam-attracting electrode 102, and focused by using the first focusing electrode 104 and the second focusing electrode 105. Then, the electron beams are deflected by the horizontal deflecting electrode 106 and the vertical deflecting electrode 107 before being landed on predetermined positions of the fluorescent layer 108. The control electrode 103 controls the electron beams over time, and adjusts each electron beam independently according to picture signals for displaying pixels.
Respective components for the image display apparatuses in the conventional technique are thin and flat plates. Therefore, an image display apparatus provided by combining these components has a thin body and a flat screen.
In the conventional image display apparatus, however, forming every electrode with accuracy is difficult, since the first and second focusing electrodes (104, 105) functioning to focus electron beams are made of conductive plates provided with slender holes, while the horizontal and vertical deflecting electrodes (106, 107) to deflect the electron beams are made of two interdigital conductive plates.
More specifically, as the first focusing electrode 104 and the second focusing electrode 105 are conductive plates provided with slender holes, waviness or warping may occur in each electrode. The horizontal deflecting electrode 106 and the vertical deflecting electrode 107 are interdigital conductive plates formed by etching plate components. Therefore, waviness or warping may occur in each interdigital conductive plate as well. Moreover, each deflecting electrode is made of two interdigital conductive plates, and thus, relative deflections may occur in the deflecting electrodes for some reason.
Tokkai Hei No. 2-33839 discloses a method for manufacturing a laminated electrode, in which the laminated electrode comprises electrodes comprising separate plural conductive plates, such as the control electrode 103 and the deflecting electrodes 106, 107. When the conductive flat plates are etched to have a slit pattern in such a case, the plates are initially etched in a continuous state. These electrode plates are adhered, laminated and fixed while being insulated in a predetermined order. After that, a predetermined part is cut by using laser beams or some other means, if insulation is required in the same surface. The process of the method, however, has some problems as follows. Pattern-etching does not support the growing demand for precision, since it is difficult to treat holes whose diameter is not more than the plate thickness or residual margins. In order to stabilize the surfaces, adhesion margins should be formed with an appropriate pitch on the entire plate surface, but this is another obstacle to precision. The plates cannot be processed to be so thin for keeping surface accuracy and stiffness, but when a thick plate is etched, the configuration at the etched section is varied, which may cause errors in electron lenses. When plates etched in different shapes are adhered and laminated, the balance in the stress is lost, and warping and waviness arise. As a result, a flat surface is difficult to obtain.
When waviness or warping arises in the focusing electrodes and deflecting electrodes composing a conventional image display apparatus, it will do harm for focusing and deflection of electron beams. As a result, appropriate control of the electron beams becomes difficult, and the landing positions of the electron beams will be deviated. In such an image display apparatus, landing an electron beam on a predetermined position of the fluorescent layer 108 is difficult. As a result, problems such as error irradiation may increase, and thus, image quality of the image display apparatus will deteriorate, and an image display apparatus with high resolution cannot be easily obtained.
In order to solve the above-mentioned problems, this invention is directed to providing an image display apparatus comprising an electrode having a flat surface free from waviness or warping. Such an image display apparatus appropriately controls focusing and deflection of electron beams and prevents problems such as deviation of the electron beam landing positions and error irradiation. The image display apparatus will have excellent images and high resolution.
In order to achieve the above purposes, an image display apparatus of this invention comprises, in a vacuum container whose inside is kept under vacuum, a fluorescent layer, an electron emission source having an electron source, and electrodes for controlling electron beams emitted from the electron emission source. In the image display apparatus in which the fluorescent layer is illuminated by the electron beams, at least one of the electrodes is formed by stringing wires on a frame of a resilient material. The two opposing sides of the frame on which wires are strung are flat plates formed on the same surface, and the electrodes are arranged between the fluorescent layer and the electron emission source.
In the image display apparatus, the frame is flat and arranged on a surface, and the electrode is formed by stringing wires on the frame. Therefore, considerably flat electrodes can be obtained without any additional processes. Such a flat electrode is free from waviness and warping, and it can control electron beams appropriately. As the frame has a certain resilience and the wires are provided with a certain tensile force by the frame, the flatness of the wires can be maintained efficiently due to the tensile force. Such an electrode can be made thin, and therefore plural electrodes can be arranged in a narrow space. Therefore, a pitch between the electrodes can be decided without limitation. As the electrode is formed by stringing wires on a flat frame, both surfaces of the frame can be used. If the frame is formed by providing a difference in level in the opposing two sides, more wire electrodes including a vertical one can be arranged in one frame. If the electrodes are used for deflection, at least the adjacent wires should be insulated so that different voltages can be applied to the adjacent wires. The flat frame can achieve such a purpose easily by printing a wiring pattern and stringing the wires to be fixed thereon. As the electrodes are composed of wires, the pitch between the electrodes (wires) can be made finer in a relatively simple manner, and thus, the resolution can be improved. In this embodiment, an image display apparatus is made by using considerably flat electrodes that can provide a fine pitch easily. As a result, an image display apparatus with excellent images and high resolution can be obtained.
Preferably in the image display apparatus of the invention, the electron source is divided and arranged in a matrix. A preferable image display apparatus of this invention has electron sources that can be driven equivalently in a matrix. There is no specific limitation on the configuration of the electron source. For example, an electron source, which is divided and arranged in stripes, or which is arranged continuously over a surface of a substrate, may be used. Any electron source can be used if it can emit electron beams in a matrix. For example, an electron emission source, which is composed of a surface conductive component composed of a thin film of SnO2(Sb) or a thin film of Au and the like or a thin film of some other material, a microchip type electric field electron emission component such as Spindt type (microchip cathode of field emission type invented by Spindt), an electric field electron emission component having the MIM type structure or the similar structure or a cold cathode ray component composed of an electron emission material which is carbon material such as diamond, graphite, DLC (Diamond Like Carbon) and the like, may be used.
Preferably in an image display apparatus in this invention, the difference between the coefficient of thermal expansion of the component where the fluorescent layer is formed and that of the frame is within 8xc3x9710xe2x88x927/xc2x0 C. in a temperature range from 0 to 150xc2x0 C. In this preferable example, even if the internal temperature rises during the operation of the image display apparatus, the deviation generated-over time between the stripe pitch-of the fluorescent layer and the wires"" pitch can be controlled within a range not affecting the practical performance of the device, since the difference between the coefficient of the thermal expansion of the component having the fluorescent layer and that of the frame is determined as mentioned above within the temperature range in the operation of the image display apparatus. As a result, the deviation of the landing positions of the electron beams at the operation can be prevented efficiently.
In a preferable image display apparatus of this invention, the frame is composed of a first frame member, a second frame member and an insulating layer, where the first frame member and the second frame member are laminated via the insulating layer, and the wires are strung on the surfaces of the first and second frame members not contacting with the insulating layer. In this preferable example, the frame is made by laminating the first frame member and the second frame member via the insulating layer. As a result, a pair of insulated electrodes (wires) sandwiching electron beams can be formed easily by stringing the wires on the respective surfaces of the first frame member and of the second frame member not contacting with the insulating layer. According to this embodiment, a pair of insulated electrodes (wires) to control respective electron beams (e.g., focusing and deflection) can be formed without carrying out additional wiring.
Preferably in the image display apparatus, the opposing two sides of the frame to which the wires are fixed are made of metal, and insulating films are formed on the surfaces of the opposing two sides. In addition, a conductive part is patterned on the insulating films, and the wires are strung to contact with the conductive parts. In this preferable example, electrodes such as a signal control electrode or other electrodes (e.g., deflecting-correcting electrode) having various voltages in the same surface can be formed with high accuracy in a relatively simple manner.
Preferably in the image display apparatus of this invention, the insulating films are formed by using a thermally-sprayed alumina layer and glass frit while the conductive parts are made of silver paste.
Preferably in the image display apparatus, the fluorescent layer is formed on the inner surface of the vacuum container. In this preferable example, the vacuum container and the fluorescent layer are integrally formed, so that the manufacturing process is simplified and the process steps can be decreased.